Failsafe system in automatic transmission

Abstract

A failsafe system in an automatic transmission includes: a device for detecting rotary speed of an output shaft of the automatic transmission; a device for detecting either rotary speed of a rotary member other than the output shaft of the automatic transmission or engine rotary speed. When a correlation between the output shaft rotary speed and either the rotary speed of the rotary member or the engine rotary speed is abnormal, control oil pressure in a hydraulic control device of the automatic transmission is increased, whereby slippage in frictionally engaging devices in the hydraulic control device of the automatic transmission during non-shift are effectively eliminated.

What is claimed is: 
     
       1. A failsafe system in an automatic transmission for a vehicle, comprising: means for detecting an output shaft rotary speed of said automatic transmission;   means for detecting engine rotary speed;   means for detecting engine load;   means for detecting whether a lockup clutch of said automatic transmission is engaged;   means for detecting whether a prescribed period of time has elapsed from either a shift judgment or a shift command of said automatic transmission;   means for determining a correlation between said output shaft rotary speed and said engine rotary speed when said engine load is higher than a predetermined value, said lockup clutch is engaged, and said prescribed period of time has elapsed from either of said shift judgment or shift command of said automatic transmission;   means for judging whether said correlation is abnormal; and   means for increasing oil pressure in a hydraulic control device of said automatic transmission when said correlation is judged to be abnormal.   
     
     
       2. The failsafe system as set forth in claim 1, wherein said oil pressure in the hydraulic control device is line pressure. 
     
     
       3. The failsafe system as set forth in claim 1, further comprising: an electromagnetic proportion valve; wherein said oil pressure in the hydraulic control device is increased by the control of said electromagnetic proportion valve.   
     
     
       4. The failsafe system as set forth in claim 1, further comprising: a duty valve; wherein said oil pressure in the hydraulic control device is increased by the duty control of said duty valve.   
     
     
       5. The failsafe system as set forth in claim 1, further comprising: means for judging whether said correlation is shifted more than a predetermined value; wherein said judging means judges said correlation is abnormal when said correlation is shifted more than said predetermined value.   
     
     
       6. The failsafe system as set forth in claim 1, further comprising: means for judging whether said correlation is shifted more than a predetermined value for a predetermined period of time; wherein said judging means judges said correlation is abnormal when said correlation is shifted more than said predetermined value for a predetermined period of time.   
     
     
       7. The failsafe system as set forth in claim 1, further comprising: a warning device; wherein, when said correlation is judged to be abnormal, a warning is issued from said warning device.   
     
     
       8. A failsafe system in an automatic transmission for a vehicle, comprising: means for detecting rotary speed of an output shaft of said automatic transmission;   means for detecting rotary speed of a turbine shaft of said automatic transmission;   means for detecting engine load;   means for detecting whether a prescribed period of time has elapsed from either a shift judgment or a shift command of said automatic transmission;   means for determining a correlation between the rotary speed of the output shaft and the rotary speed of the turbine shaft when said engine load is higher than a predetermined value, and said prescribed period of time has elapsed from either of said shift judgment or shift command of said automatic transmission;   means for judging whether said correlation is abnormal; and   means for increasing oil pressure in a hydraulic control device of said automatic transmission when said correlation is judged to be abnormal.